The system is referred to as a "Selector Valve" system. If the rooms are of different sizes, and you only have one (1) cylinder, check the concentration of smaller rooms and make sure it doesn't exceed the maximum concentration limits as prescribed by the given standard (i.e. NFPA 2001). If the room sizes are drastically different, you may want to find the common denominator. for the agent concentration and use multiple cylinders.
So...if one room takes 400 lbs of agent, and the other room(s) take 200 lbs, use two (2) cylinders with each cylinder filled to 200 lbs.
You'll likely have other issues however. Just because the math works, doesn't mean the hydraulics' will work. Selector valves impose a significant equivalent length in the piping system.
There are two (2) manufactures (in the USA) that have systems with sufficiently high enough pressure to overcome the equivalent lengths of the selector valves. They are:
Kidde with their "ADS" (Advanced Delivery System).
Minimax with their high pressure systems (720 PSI).
If you're specifying a system, I would suggest you contact a company that can run the calc's and verify that it's possible "Hydraulically". At some point the costs can become prohibitive.
Regards,
DM
"Real world Knowledge isn't dropped from a parachute in the sky but rather acquired in tiny increments from a variety of sources including panic and curiosity."